1. Field of the Invention
The present invention relates generally to fluid-filled vibration damping devices capable of exhibiting damping effect on the basis of flows of the fluid sealed therein, and more particularly to a fluid-filled vibration damping device suitably applicable to engine mounts or other mounts for use in automotive vehicles, for example.
2. Description of the Related Art
Rubber vibration-damping devices, typically including a first and a second mounting member elastically connected via a rubber elastic body, have been widely been used in a variety of fields, as vibration damping couplings or mounts to be interposed between two members of a vibration system. In an attempt to enhance vibration-damping effect, it has been developed a fluid-filled vibration-damping device capable of exhibiting damping effect with the help of resonance or flows of non-compressible fluid sealed therein. Generally, such a fluid-filled vibration damping device is of construction further includes: a pressure-receiving chamber partially defined by the rubber elastic body in order to induce a fluid pressure variation upon application of vibration thereto; an equilibrium chamber partially defined by a flexible layer in order to permit a volumetric change thereof; and an orifice passage for permitting a fluid communication between the pressure-receiving chamber and the equilibrium chamber.
Typical examples of such a fluid-filled vibration damping device are disclosed in the Reference Nos. 1–5 listed herein below, which are applied to an engine mount, a body mount, and other mounts for use in automotive vehicles, for example.
[Reference 1]    JP-A-57-9340
[Reference 2]    JP-B-7-54131
[Reference 3]    JP-A-10-184769
[Reference 4]    JP-A-3-177635
[Reference 5]    JP-B-5-55739
An extensive study and analysis conducted by the inventors on these conventional fluid-filled vibration damping devices revealed that these conventional fluid-filled vibration damping devices may cause noises or vibrations in the event of input of a relatively large vibrational load between the first and second mounting members. Specifically, when being employed as an engine mount in an automotive vehicle, the conventional fluid-filled vibration damping device may generate noises or vibrations large enough to be sensed by passengers in a cabin of the vehicle, if the vehicle runs across a wave-type road, or alternatively runs over a speed breaker or the like.